Card Readers

I have been using a very compact Butterfly Media card reader. It has worked fine until I started taking large TIF and RAW photos. When I tried to download and open a file, it showed the file to be "broken or unreadable". My CF card is a new 512mb 25x and I was suspicious of it, but when I connected the camera directly to the computer, it worked fine. Has anybody else experienced this problem?

Also has anybody tried the firewire port to download files from the camera and if so, is it a lot faster?